1. Field
The present disclosure relates to a non-aqueous electrolyte secondary battery, in particular, to a lithium ion battery.
2. Description of the Related Art
It is known that, in non-aqueous electrolyte secondary batteries, phosphorus-containing compounds are used as a flame retardant for suppressing an exothermic reaction between a positive electrode active material and an electrolytic solution that is a non-aqueous electrolyte in liquid form. Japanese Patent No. 3131905 discloses that a phosphoric acid ester is dissolved at 15% by mass or more relative to the total mass of an electrolytic solution to thereby suppress an exothermic reaction between a positive electrode active material and the electrolytic solution.